Magnesium base alloy



Patented Nov. 12, 1940' UNITED STATES MAGNESIUM BASE ALLOY John C. McDonald, Midland, Mick, assignor to The Dow Chemical (iompany, Midland, Mich, a corporation of Michigan No Drawing. Application November 13, 1939, Serial No. 304,132

3 Claims;

. The invention relates to magnesium base alloys. It more particularly concerns alloys of this nature having a high degree of formability associated with other improved physical properties, such as increased tensile and yield strengths.

Magnesium alloys are being widely used in various structural and mechanical arts where a light weight metal is highly desirable, such as for use in making castings, forgings, and the like. 10 However, the use of these alloys in the rolled form to make sheet metal article-s requiring forming operations, such as bending, drawing, or the like, has not progressed as rapidly due to the fact that, in general, alloys of good formability permitting relatively sharp bends to be made without the article developing external cracks have inferior characteristics as regards their tensile and yield strengths.

It is, therefore, the principal object of the in- 20 vention to provide a magnesium base alloy which may be made into rolled sheet or the like, possessing a sufficient degree of ductility or formability to be sharply bent, drawn, or otherwise yield strengths, are manifest over the entire range of composition indicated, I have found that,

in general, the preferred combination of properties, such as the most desirable ductility for forming operations coupled with high tensile and 5 yield strengths, is obtained when the alloy contains from 2 to 5 per cent of silver, from 6 to 8 per cent of cadmiufn, and from 1.5 to 2 per cent of manganese. Alloys containing the higher percentages of alloying ingredients, while still hav- 10 mg good forniability, have exceptionally high tensile and yield strengths, thus making them very suitable for use in casting operations as well as foriorming operations.

The following table, which lists some of the properties of rolled sheet metal made from my new, alloy, as well as the properties of rolled sheet metal made from the related ternary alloys, illustrates the improvement in strength properties of the new alloy over the closely related alloys. In the table the present elongation is to be regarded as an expression of the ductility or formability of the alloys,

Table Nominal com siti n in percent (re m ain%er= Annealed Cold rolled magnesium) Yield Tensile Percent Yield Tensile Percent Ag Cd Mn strength in strength in elongationin etrengthin strength in 01011 ation in lbs./sq.ln. lbs./sq.in. Zinches lbs./sq. in. lbsJsq. in. 2 nehes shaped, while having high tensile and yield The properties listed in the above table under strengths:- Y the section headed by the term annealed were 45 Other obJects and advantages will be apparent obtained by first rolling the alloys at a temperas the description of the invention proceeds. ature between about 600 to 800 F., and there- My invention resides in the discovery that a after annealing them at various temperatures magnesmm base alloy composed of from 0.5 to 10 through a temperature range of from 400 to 800 per cent of silver, from 1 to 15 per cent of F. The properties selected for the table were 50 cadmium, and from 0.1 to 3 per cent of.,manganese, the balance being substantially all magnesium, is endowed with the afore-mentioned properties. While the properties of good formability, together with increased tensile and those of the annealed specimens which exhibited the maximum elongation. The properties listed under the section headed cold-rolled were obtained by subjecting specimens of the alloys which had .been hot-rolled at a temperature of above table, it will be observed that the combined properties of my new quaternary alloys are superior to those of the parent ternary alloys .having similar percentages of alloying ingredients. For example, it will be noted that in the lower percentage of alloying ingredients, the new alloy not only has a higher degree of elongation which is a measure of its ductility or formability, but it also has improved tensile and yield strengths. In the higherpercentage range of composition, it will be noted that the elongation is still fairly good, while the strength characteristics of the alloy in both the annealed and the cold-rolled state, are much superior to those of the parent alloy.

While the new alloy is most useful in wrought form, such as sheets, due to its formability characteristics, it may also be suitably used in makiiig castings, forgings, extruded forms, and the like. It is further pointed out that my new alloy is amenable to solution and precipitation heat treatments, which, accordingly, modify its properties.

The new alloy may be compounded by any of the methods usually employed for melting and alloying metals with magnesium, such as by adding the alloying materials singly or jointly to a bath of molten magnesium, which is preferably protected from oxidation by a suitable flux.

I claim:

1. A magnesium base alloy containing from 0.5 to 10 per cent of silver, from i to 15 per cent of cadmium, and from 0.1 to 3 per cent of manganese, the balance being magnesium.

2. A magnesium base alloy containing from 2 to 5 per cent of silver, from 6 to 8 per cent of cadmium, and from 1.5 to 2 per cent of manganese, the balance being magnesium 3. A magnesium base alloy containing 3 per cent of silver, 7 per cent of cadmium, and 2 per cent of manganese, the balance being magnesium.

JOE? C. McDONALD. 

